Before a snapshot appears on a display of a digital camera, a lens in the camera focuses an image onto an optical sensor made up of an array of photo-detectors. This array of photo-detectors converts the light of the image into electrical signals that are used to generate a digital encoding of the image.
Conventional optical sensors are less than ideal for several reasons. For example, conventional optical sensors do not absorb light as accurately as possible, due to scattering or radiative transitions re-directing photons away from the photodetectors. Further, because individual photo-detectors are often, in-and-of themselves, unable to differentiate between different colors of light, color filter arrays (CFAs) with separate color filters for red, blue, and green light are often arranged over photodetector arrays. As shown in FIG. 1A-1C, however, these conventional color filters are less than perfect. Whereas an ideal blue color filter (transmission spectrum 102) would allow perfect transmission of visible blue light while perfectly attenuating other portions of the electromagnetic spectrum as shown in FIG. 1A, conventional blue color filters (transmission spectrum 104) block some blue light and allow other portions of the electromagnetic spectrum to pass. As shown in FIG. 1B, the same is true of conventional green color filters 106 (compared to ideal green color filters 108); and as shown in FIG. 1C is also true of conventional red filters 110 (compared to ideal red color filters 112).
Consequently, the present disclosure provides improved optical sensors that make use of plasmonic nanostructures. These plasmonic nanostructures can be used to better confine the light impingent towards the optical sensors, and/or can also be used to better filter the light provided to the optical sensors.